If you have experience problems with your Samsung Galaxy S4 Zoom, for example the smartphone freezes (hangs) or has fatal errors, you must reset the phone. If your phone is frozen and unresponsive, press and hold the Power button for more than 7 seconds. The smartphone reboots automatically.
If the above methods does not work properly, you can perform factory data reset. Follows this instructions: On the Applications screen, tap Settings→Accounts→Backup and reset→Factory data reset→Reset device→Erase everything.
The above methods described in the operating manual for Samsung Galaxy S4 Zoom (SM-C101). You can read on page 165 and you can download the user manual in pdf format here.